The present invention relates to a nematic liquid crystal cell weakly doped by a chiral solute and of the type having electrically controlled birefringence. It particularly applies to the production of means for the display of fixed or moving images or pictures.
Nematic liquid crystal cells are known, which utilize the electrically controlled birefringence effect. Such cells suffer from the disadvantage of requiring expensive circular polarizes to enable them to function correctly.
Liquid crystal cells are also known, which have a nematic liquid crystal coating to which a dichroic dye is added and which are highly doped by a chiral solute, in such a way that the resulting cholesteric liquid crystal twist is roughly the same as the thickness of the liquid crystal coating. In order to function, such cells use the selective absorption of the dichroic dye in unpolarized natural light and the "white" and "black" states of said cells respectively corresponding to the very different tilts of the molecules in said cells. In the centre thereof, the tilt is approximately zero degrees for the white state and approximately 70 to 90 degrees for the black state.